Standardise header guards across codebase

All identifiers, regardless of use, that start with two underscores are
reserved. This means they can't be used in header guards.

The style that this project is now to use the full name of the file in
capital letters followed by 'H'. For example, for a file called
"uart_example.h", the header guard is UART_EXAMPLE_H.

The exceptions are files that are imported from other projects:

- CryptoCell driver
- dt-bindings folders
- zlib headers

Change-Id: I50561bf6c88b491ec440d0c8385c74650f3c106e
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
diff --git a/plat/hisilicon/hikey/include/hisi_mcu.h b/plat/hisilicon/hikey/include/hisi_mcu.h
index f5c6ed0..731c51a 100644
--- a/plat/hisilicon/hikey/include/hisi_mcu.h
+++ b/plat/hisilicon/hikey/include/hisi_mcu.h
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
-#ifndef	__HISI_MCU_H__
-#define	__HISI_MCU_H__
+#ifndef HISI_MCU_H
+#define HISI_MCU_H
 
 #include <stdint.h>
 
@@ -13,4 +13,4 @@
 extern void hisi_mcu_start_run(void);
 extern int hisi_mcu_load_image(uintptr_t image_base, uint32_t image_size);
 
-#endif	/* __HISI_MCU_H__ */
+#endif /* HISI_MCU_H */